In domestic hot water systems, a water supply is connected to the cold water side of a hot water heater. In addition, the supply connects to all cold water outlets. Examples are cold faucets in lavatories, showers, bath tubs, and commodes.
The hot water side of the water heater is connected to all hot water outlets. Examples are hot faucets in laboratories, showers and bath tubs. Often both the hot and cold water lines are connected to respective sides of single handle mixer valves.
Also it is common for one water line to branch into a number of branch lines. One such example is for one bathroom to have its lines divided individually to supply the lavatories, shower and tub.
It is common practice for the hot water lines to be stagnant when the hot outlet valves are closed, and cover a period of time the water in that line will cool. Then when the hot water is turned on, cold water (or at least water not as hot as the heater supplies) will first be released. The conventional response to this situation is to let the water run until the hot water pipe to that outlet is purged of the cold water and is replaced by hot water from the water heater. This results in wasting the "slug" of water which was contained in the hot water line downstream from the water heater. It simply goes down the drain.
Such wastage has been conventionally acceptable for many years. Now, however, water supplies are much more sensitive to useless wastage than they formally were. Especially during times of drought, such wastage can be very expensive. In regions of very short water supplies, such as in remote well-based systems, such wastage is impermissible.
There are, of course, hot water recirculation systems which continuously circulate hot water so that the water in the hot water lines cannot cool. Hot water circuits in quality hotels and extra-quality homes frequently have these systems. Their penalty is the need for a second pipe loop for recirculation purposes, and the need to recirculate all of the water in the hot water circuit. The expense of the loop and of the continuing energy use are luxuries whose cost is not generally affordable.
It is an object of this invention to provide a purge system which purges a slug of cooled water downstream from the water heater an injects it into the cold water system without loss of water. This is accomplished in close adjacency to two faucet outlets in a branch from the main lines. The energy required is only that which is needed for pumping a rather small volume of previously-heated water, mostly in the branch line, from the hot water system into the cold water system, against only a trifling pressure differential.
The penalty is only that of waiting a few moments for this purge action to cause a replacement slug of hot water to enter into the hot water line to replace the purged water, and this will often take less time than would be required for the cold slug to be wasted through the hot water valve.
The savings of water and energy over the known art and practices, while small for each actuation do add up, especially when excessive use of water is heavily penalized. Also, it requires little plumbing, and in fact can be installed by anyone with rudimentary plumbing skills.